Process of cracking hydrocarbons by means of catalysts



Nov. 2, 1937. F. sgcHlcK Erv AL 2,097,939

EHOCESS OF' CRACKNG'." HYDRCARBONS? BY' MEANS 0F CATLYSTS Filed June 8., 1953- 'Patented Nov. 2, 1937 PATENT oFFlcE PROCESS F CRACKING HYDROCARBONS BY MEANS OF CATALYSTS Friedrich Schick and Eugen Emilius, Berlin- Mariendorf, Germany, assignors to th Firm Deutsche Erdl-Aktiengesellschaft,

erlin- Schoneberg, Germany Applicatiolllil June 8, 1933, Serial No.

Germanylune 9, 1932 4 Claims.

It is old to conduct hydrocarbons in gaseous form, if required in conjunction with carrying gases or steairi,V over coke residues of various kinds', such as pit coal coke, senil-coke or lignite' 5l coke, or activatedcharcoal. In particular it has been suggested transform or crack hydrocarbon mixtures with high boiling points, such as mineral oils, tars and similar substances, into products with low boiling points, as for instance 1Y0 motor fuel or gasoline. I

The feasibility of suoli cracking processes is, however, adversely iniiuenced on the one hand by the fact that the catalysts in part possess merely alimited cracking capacity; on the other l5 hand, by the fact that the starting materials or the mode of operating upon them would prove too expensive for obtaining highly active catalysts therefrom, and nally by the fact that the eilectiveness of the catalysts rapidly declines in use. The regeneration of the catalysts by gases and vapours merely insures a limited degree of eiectiveness, which also drops ofi' within a short time. We now have found, that the capability of the coke residues for cracking hydrocarbons is very 5 considerably enhanced not only with regard to' the initial activity, but also to the duration of eiciency by a far reaching elimination of the ash content of the coke residues obtained from mineral coals. The' elimination of theash content may be effected .by treatment with acids, e. g. Vhydrochloric acid, and by the extraction with Water. Further we have found, that such a treatment will be more effective, if it is carried out in conjunction with an activation by means of suitable gases or vapours, and especially after such a treatment. The reason for the favourable eiect 0f the elimination of ash in conjunction with a previous activation may possibly be looked for, on the one hand, in the fact that the ash-containing coke will be much more activated than the'coke from which the ash has been previously eliminated, owing to the intensification of the reaction of the carbon (particularly that with steam) by the ash, and, onl the other hand, in that by the previous activation, probably mainly in consequence of a reduction, the ash content becomes more soluble and the coke is rendered more accessible to the extraction means for the elimination of ash due to the increased porosity of the activated coke. 'I'he treatment by means of steam at temperatures up to 650 C. was found to be a favourable one for the elimination of ash and simultaneously for the activation. 55. We have further found that it is particularly advantageous to start, in the characterized production of cracking catalysts, from such distilla- -tion residues or coke residues which have been obtained under moderate conditions and also in avoiding local overheating, for which purpose especially the smouldering process or process of incomplete combustion Working with scavenging gases under the conditions of low temperature or p distillation by internal heating by means of a current or hot inert gas may be employed.

The indicated combined treatment of activation by'means of water vapour with subsequent eliminationof the ash of the coke renders it also possible, if a suiiiciently firm coke is used as starting material, to produce rm, large-sized cracking catalyzers up to approximately the size of the original coal briquette used, e. g. 38 x 50 x 50 millimeters, said catalyzers possessing a low percentage of ash, for instance only 4%, and a. high cracking activity. A cracking catalyst of such kind may, for instance, be obtained by means of a certain addition of caking to non-'caking coal, or by the employment of other, also liquid, solidifying agents, such as asphalt, or by drying the starting coal so as to have a lower percentage of water than the ordinary briquettes placed on the market, or else by employing such pit coal or brown coal or lignite, which by their nature furnish particularly iirm coke. k

The methodv oi' carrying through the process and the advantages connected therewith will Vbe elucidated by means of the following examples of execution and comparative experiments:

Semi-coke from brown coal or lignite of Central German origin mined in the district south of Borna, obtained in a large cokng or distillation plant at a temperature of about 550 C. b y means 0f scavenging or inert gas, screened down to a grading of 4-7 mms. diameter and having a content of ash of 18%, 1% of which consists of alkalies and 40% of which consists of alkaline earths, is,,treated31531146223C.v with well distributed steam/untilthe capacity of methylene blue adsorption of the material has been increased 10 4to l5 times the original amount. i. e. during abou 2-3 hours. By extracting with aqueous hydrochloric acid and washing with water in conjunction with partial neutralization with ammonia, the ash is reduced down to a residual percentage of ashes of about 5%. Subsequently the obtained coke product is dried at a temperature of about 400 C.

With the aid of the catalyzing material thus obtained, the cracking ofoils of different kinds 95.11 be carried out in such a manner that. after atomized by means of of superheated steam, their temperature being raised thereby to about -400 C. and by further admixture of gases free from oxygen to about 450 C. 'I'he direct heating of the mixture of oil and steam may for instance be eiected by means of the ilue gases of a burner heated by Weak gases, the flame temperature of said flue gases of about 1100 C. being cooled down to about 550 C. with the aid of water or steam sprayed in. The oil vapour,

being diluted about twentyfold by' steam and iiue gases, passes through the chamber containing the catalyst at a velocity of about 4 to 5 liters (at 450 C.) per square centimeter of the cross section and per minute, the temperature of. said chamber being maintained at a constant levelby indirect heating by means of an electric current or gas circulation. By a single passage of a gas-oil having a speciilc gravity of .845 through a catalyzing path of 70 centimeters length, 40% of gasoline is obtained. When three such catalyzing paths are arranged in series and the gasoline formed is intermediately withdrawn, a total yield of about gasoline and 20% of residual oil is obtained. In the same manner 50%of gasoline and 20% cf residual oil may be obtained from a heavy petroleum fraction (specinc gravity- .900).

In a similar manner, lignite tar-oil'rof` .845 specific gravity preliminarily treated by the socalled Edeleanu process, may be processed contin'ucusly v*with only the addition of steam to the starting oil, usingy a semi-coke or coke breeze freed from ashes down to 3.2% by means of hydrouoric acid as splitting catalyst, the yield of gasoline even after several days of working, showing a decrease of only 10% compared with the average yieldl of 35%. The feed of oil in this process needs only to be interrupted for' short periods, during which intervals steam alone is conducted over the catalyst at a temperaturevoi' about 600 C.

The ameliorating iniluence of the elimination of the ashes upon the cracking activity' of the catalysts is proved for instance by the comformed under identical conditions with the only difference, that in the one case an activated semi-coke free from ashes is employed whereas in the second case a cracking catalyst is used which has been produced in the same manner, from which, however, the ashes have not been eliminated. An average increase of of gasoline output is obtained in the rst case,l e. g. from 23% to 40% for a catalytic path of l'Z0 centimeters length and a temperature of about 450 C. Even greater increases in yield may yet be observed.

The further, still more valuable progress attained with the laid of the present process, viz, the better' maintenance ci the activity of the catalyst, is manifested in the above mentioned continuous experiment with refined lignite taroil by the fact, that, when employing a catalyst freed-from ashes, a Waste of only 10% is re. corded, Whereas when employing a catalyst from which the ashes have not been eliminated, this waste rises to about 35%. 'I'he greater durability of the catalysts low in ash content have proved themselves, using the most varied starting materials and under varying conditions, even more conclusively than in the foregoing example.

The inuence of the kind of the dry distillapreliminarily heating to about 350 c., they are tion process, employed for the starting materials, upon the cracking eiilciency of the coke residues obtained thereby, is shown for instance by the yields of gasoline which are attained by the employment of cracking catalysts prepared inthe same manner from different coke products and used under identical cracking conditions for the treatment of the above mentioned refined lignite tar-oil: When a brown coal or lignite coke is employed as starting material which was obtained in a Rolle plant or kiln at a temperature of about '150 C. or in gas retorts at a temperasteam at 850 C. and subsequently freed from ashes reduces the yield of cracking products by about 30% when compared with that obtained by means of a cracking catalyst activated at a temperature of only 625 C. but otherwise prepared under identical conditions. The fact that the cokes produced or subsequently treated at a higher temperature are of less suitability for the purposes mentioned herein, will be caused by that the processor elimination of the ashes therefrom is rendered more diicult by said higher heating temperatures. Thus the elimination of the ashes under identical conditions after activation with steam from the previouslymentioned brown coal or lignite coke produced at a temperature of 850 -C..causes the percentage of ashes to drop from 21 to '1% and for a, high temperature coke obtained from bituminous pit coal from 12 to 8%, whereas for a semi-coke or coke breeze gained from brown coal or lignite under low temperature conditions by means of scaveng- 'ing gases the percentage of ashes drops from 28 to 4%. I

The importance of the advantage which will be attained if the activation with steam precedes the elimination of the ashes, is proved by the fact that, starting from the same brown coal or lignite semi-coke or cokebreezethe immediate eliminm tion of the ashes will leave a residue of 11% of ashes inthe coke, lwhilst the same method of eliminating the ashes after the activation with steam will reduce this ash content to 4%, although the preliminary activation brings about in the first instance even an enrichment oi ashes.

Forithe purpose of supplementing the data recorded in the foregoing, the following general Y indications concerning the method of carrying out the present process are given. i

Well adapted conditions are: the use of cracking temperatures of from 300 to 500 C.; lengths of the catalyst path between 6 and 0.1i meters; the use of steam up to 200% as accompanying gas; the useof linear velocities from 50 to 300 liters per m2/sec. (referred to 20 C.) for the mixture of oil and steam to be treated.

The increase of capacity oi! the cracking device may bev still further enhanced very considerably by limiting the quantity tog the accompanying gas, and it has been found at, provided a suitable velocity is used, oil vapour alone may be employed, a satisfactory yield of gasoline nevertheless obtained. For instancein conjunction with the above mentioned gas-oil, an average yield of gasoline of about 25% was ascertained when using a linear velocity of't/mz/h and a temperature of 450 C. for a catalytic path of 0.7 meter length. If no steam or the like is to ,be admixed or only a small quantity thereof, the oils may be finely divided by means of an atomizer, or, after being preliminar-ily heated with the aid of a tubular heater they may be evaporated in a boiler, simultaneously eliminating the distillation residues.

The attached drawing shows one embodiment' of the device, partly in section, to be employed for executing the described process, wherein preheated oil is brought to cracking temperature either directly by means of steam or by indirect heating.

In this drawing 9 is an oil pump, I a preheater coil for the hydrocarbon oil to be treated, l a pipe for introducing steam, 8 a pre-heater coil for the steam, 2 a superheating device for the steam', and 3 the chambers for cracking the oil to be treated, said chambel being filled with the contact material or catalyst 5 in question. In the embodiment shown three chambers 3 are arranged 4the one vertically above the other, said chambers being connected with one another by the connecting pipes shown, which contain three-Way `cocks in such an arrangement that the three chambers may be connected in series or parallel to one another at will, as desired. The catalyst 5 is arranged on perforated members i within the chambers 3, and its grains have a size of about to millimeters in diameter. The `temperatures are kept constant by means of electrical heating elements 5 and the temperature is measured by thermo-couples 4 The oil or oil and'vapour are introduced into tl.: chambers 3 by means of mixing or pressing nozzles, not shown. The device allows one or two of the chambers 3 to be set out of operation for the purpose of regenerating the catalyst contained therein, whereas the others or the other chamber, respectively, remain in operation during this time. A special pipe may be arranged for the removal of the vapour employed for regenerating the catalystwithin said chambers.

Furthermore, the oils may be de-sulphurized in vaporized state in a known manner prior to entering the catalytic zones, or even between some i of these zones or after leaving them. Moreover,

substances having the tendency to polymerize, or, if necessary, coarse particles may be removed before entering or between the cracking zones, by passing the vapours over used cracking catalysts or other porous bodies, preferably such, whose cracking activity is of a low degree. It may furthermore prove of advantage. to withdraw from between the separate catalytic steps certain portions of the reaction mixture and, respectively or, Aadd carrier gases or oils or oil vapours to the reaction mixture.

The activation prior to the elimination of the ashes may also be effected with the aid of an impregnation by means of alkalis or alkaline earth bases, preferably the former. 'I'he elimination of the ashes may be effected in steps by several, different means, e. g. different acids, if desired also with water only. The elimination of the ashes being heated for instance during the drying of the coke residues freed from ashes.

The elimination of the ashes with the aid of sulphuric acid, which embodies certain advantages, may be carried through in suchV a manner, that after the characterized activation with steam the product is lrst extracted with water, then treated, with diluted sulphuric acid, subse quently is reduced by means of steam or watergas or by both, and the series of operations being closed by another extraction with water. In connection herewith that water-gas may be employed, which is produce"1 in conjunction with the activation by means of steam.

If desired, the acids may also be employed in a gaseous state. y

It should be pointed out that no connection exists between the methylene blue discolouring and the cracking capacity of the catalysts used, particularly with respect to their ash content.

The far-reaching influence of the elimination of the ash upon the catalytic effect in connection with the present process is surprising from several points of view. It 'is a known fact. that an acceleration of the cracking reactions to be considered quite generally takes place on bodies providing a large surface, and several processes utilize this principle by distributing nely divided inorganic oxides and salts, among others, also such, which are precipitated on active coal. The

lspecial effect of the preliminarily treated coke or distillation residues by the elimination ofthe ash was, therefore, not to be expected. because, according to the latest scientic views, on the contrary, a favourable effect ofthe components ofthe ash from semi-coke or coke breeze upon the cracking of liquid hydrocarbons, for instance in the manufacture of motor oils and the like from distillation tar, had been assumed. As

used in the claims the term heavy hydrocarbons has its usual significance in the art, viz., hydrocarbons boiling in the gas-oil range or at higher temperatures.

Having now particularly described and ascertained the nature of our said invention, we declare that what we claim isz-'- 1. The process of cracking heavy hydrocarbons to produce lower boiling hydrocarbons comprising preliminarily purifying said heavy hydrocarbons and thereafter conducting them while heatedover catalytic paths of from 0.3 to 6 meters length at temperatures of from 300 to 500 C. and at a velocity of from 50 to 300 liters per square meter of cross-sectional area of reaction chamber, per second, said catalytic paths being composed of coke residues of mineral coals which have been activated by means of steam at a temperature up to about 650 C. and have a low ash content.

2. The process of cracking heavy hydrocarbons to produce lower `boiling' hydrocarbons com' prising preliminarily purifying said heavy hydrocarbons in thepresence of admixed gases `which remain inert underthe employed conditions, and thereafter conducting them while heated over catalytic paths of from 0.3 to 6 meters length at temperatures of 'from 300 to 500 C. and at a velocity of fromf50 to 300 liters per square meter of cross-section .area of reaction chamber, per second, said catalytic-paths being composed of coke residues of mineral coals which have been activated by means of steam at a temperature up to about '650 C. and then have been treated to to produce lower boiling hydrocarbons, comprising preliminarily purifying said heavy hydrocarbons in the presence of admixed superheated steam,` and thereafter conducting them while heated over catalytic paths of from 0.3 to 6 meters length at temperatures of from 300 to 500 C. and at a velocity of from 50 to 300 liters per square meter of cross-sectional area of reaction chamber, per second, said catalytic paths being composed o1' coke residues otmineral coals which have been activated by means of steam at a temperature up to about 650 C. and have been treated with acids and water to reduce the l. ash content to a low value'.

4. In the process of cracking heavy hydrocarbons to produce lower boiling hydrocarbons, the steps of conducting the hydrocarbons through catalytic paths of `from 0.3 to 6 meters length at temperatures of from 300 to500 C. and at a velocity of i'rom 50 to 300 liters per square meter of cross-sectional area of reaction chamber per second, said catalytic paths 'being composed of coke residues ot mineral coals which have been activated'by means'oi. steam at a temperature up lo to about 650 C. and have a low ash content.

1 FRIEDRICH scmcx.

EUGEN mimos. 

